There is no electrical sensor in that location... p e r i o d. K?
Get a decent photo of all the sensors on that thermostat tower (both sides) and we'll see if we can't figure out what they were thinking and what needs to be fixed.
To you have any aftermarket gauges or a turbo timer with a temp sensor?
With the block off plate you want something at least 1/8" (3mm) thick, preferably 1/4" thick. Take the Oil line in to a parts store and look among the Chevy block off plates.. there should be something close enough; You may need to oval out the holes a bit to get it over the studs on your engine, but it'll work fine. USE A GASKET!!!!
When you press the gas pedal more than 70% the ECU will go into closed loop... it's not reading the O2 sensor at this point and is going to be pretty rich. It's still measuring airflow though, so for the most part it should be alright. I'd avoid pounding on it too much though. If you run rich too much you'll foul the O2 sensor and foul and clog the cat. You may see engine error codes though which may throw you into "limp mode" due to the unexpected airflow drop at certain throttle levels and RPMs. Codes 25, 26 and 34 are the ones to watch for if the car suddenly stops responding beyond 2500 - 3000RPM and runs richer than hell. In this case reset the ECU (by pulling the EFI fuse for 10 seconds) and start driving like a granny.
